1. Field of the Invention
The present invention relates to connection of a branch element such as a branch pipe or branch fitting to a high pressure fuel rail such as a high pressure fuel line or block and in particular, to a branch connection adapted to inject fuel to a gasoline engine and particularly, to deliver fuel under a pressure of greater than 1000 kgf/cm.sup.2 to a diesel engine.
2. Description of the Prior Art
A conventional branch connection is exemplified, for example, in FIGS. 12 and 13. A main pipe 11 has an inner bore or passage 12. A plurality of conical or arcuate pressure receiving surfaces 13 are formed in the circumferential wall of the main pipe 11. A branch pipe 15 has a conical or arcuate end or press head 16 engaged in the corresponding pressure receiving surface 13 of the main pipe 11. A seal 14 is in the shape of a bowl and is disposed between the pressure receiving surface 13 and the press head 16. The seal 14 includes a central straight hole 14' and a bent wall 14" extending inwardly from the central hole 14'. Upon securement of the branch to the main pipe, a space 17 is defined by the bent wall 14" of the seal, the peripheral edge of the pressure receiving surface 13, and the passage 12.
In such a connection, however, a high pressure of greater than 1000 kgf/cm.sup.2 is applied to the seal 14 to provide two components P.sub.1 and P.sub.2. The component P.sub.2 is a force (fluid pressure x sin .theta.) applied to separate the seal from the pressure receiving surface 13. This force, together with vibration of an engine, causes fuel to enter between the seal 14 and the pressure receiving surface 13 and thus, leak from the main pipe.